1. Technical Field
The present invention relates generally to electrical circuit and in particular to voltage regulators and designs thereof.
2. Description of the Related Art
Conventionally, output impedance and thus output voltage of load regulator devices fluctuate due to one or more of a plurality of factors, including changes in temperature or other operating environmental conditions, and/or changes in current, etc. experienced by the circuit. Voltage (or load) regulation, which measures and counters variations in regulator output voltage due to changes in loading is conventionally dependent on output impedance. Those skilled in the art of electrical circuits and circuit design appreciate the need/desire for accurate, linear output characteristics of load/voltage regulator circuits/devices.
In integrated circuit (IC) chip design, for example, the circuit devices that make up the IC chip typically require a pre-set amount of input voltage (falling within some definable range of acceptable voltage) for proper operation of the devices. To reduce the effects of various nonlinearities which otherwise adversely impact the accuracy of the output voltage, most conventional voltage regulator circuits implement negative feedback to set the output voltage. The negative feedback utilizes open loop gain to lower the output impedance and improve load regulation, increasing accuracy of the output voltage. In addition to increased accuracy, negative feedback also lowers other nonlinear effects and improves line regulation, a measurement of the variation in regulator output voltage due to changes in input voltage.
With conventional voltage regulators, certain tradeoffs must be made when implementing negative feedback. Among these tradeoffs are: (1) accuracy of output voltage versus non-linear environmental/circuit factors (e.g., supply/process/temperature); (2) unconditional stability of the feedback loop which yields acceptable Phase/Gain margin and prevents oscillation; and (3) low PSRR (Power Supply Rejection Ratio), a measurement which tracks how much the output moves due to movements in the input supply (observed effects of an AC supply source and/or noise on the input)
With conventional voltage regulator circuits, it is difficult to satisfy all three tradeoffs simultaneously, particularly over a wide input voltage range. However, such a circuit would be extremely desirable.